Formic acid.



UNITED STATES- PATENT ornron'.

HENRY HOWARD, or BOSTON, un'ssAdnusErIs.

Fomvuc lion);

Specification of Letters Patent. Patentd-N ov, 151910;

No Drawing; Applic ation'filed March 24, 1908,-- S'eria1 m; maooc. Renewed September so; 1910. Serial nasaueo.

To all whom it may cone-cm: 1

Be it known that I, HENnY HOWARD, a

citizen of the United States, residing at Boston, in the county ofSufiolk and State .5 of Massachusetts, have invented certain new and useful Improvements in Methods of Producing Formic Acidfof which'the following is aspecification.

Thexobject of this invention is to provide 1 an efiicient method of producing formic acld from formate'sfl -It has been'proposed here-j tofore' to dissolve srdiuinformate'in highly concentrated form c acid,- ;and-to decompose. I the f nmate-by adding to the solution sul-- .furic acid or an acid sulfate. It has likew se been proposed tomixafdry formate with an acid sulfate, and to distil formic acid from the mixturez, I-ghaye" now discovered that formic acid-imaybe'readily produced,' with I high s.eifici encyand without the necessity of s operating-fin pifesence-ofprevi sly preparedformieacid, .y reacting on afor'mate, usually sodium '"f ormate, in presence of-water,

' with a'gaseous reagent capable of liberating formic acid, preferably with sulfur trioxid in presence. of sufficient water to'convert the sulfur .trioxid'into sulfuric acid;

I may proceed substantially as; follows:

- Gaseous sulfur trioxid isconducted intoa. 'vessel contalning-sodlum formate or'other suitable salt 'of formic acid, in-presence of sufficient water to combine with the sulfur.

trioxid with formation of sulfuric acid, the water being destributed with subs antlal uniformity-throughout the massiof f innate.

' .Thezmoist formate is. preferably, stirred.

' heating. 'Moreover the rate-of reaction may be accurately controlled by the rate of ad- :mission of sulfur trioxid to'the'vessel. The formic acid produced will be highly conc entrated'in case the water present is suffi- L cient onlyto combine with thesulfur trioxid used, although obviously acid of any deacid is recovered by distillation or otherwise as may bedeslr'ed.

vA particular advantage of the method-.

above described lies in the fact that' tl-igerei" is little or no liability to a loss of product due to local over-heating. When. concentrated sulfuric acid is added to sodium formatefiit is necessarily present. at first in local excess, and acts injuriously upon the formate or formic acid produced therefrom.- If however the formate, preliminarily moistened, be exposed to gaseoussulfur trioxid the production of'sulfuric acid occurs uniformly throughout the'mass and there is at no time such local excess as is capable of exerting any injurious efiec't. v

While I prefer to use sulfur trioxid as the gaseous reagent for decomposing the moist formate, I may-employ other gaseous reagents which are capableof liberating formic acid,'as for instance g'aseous hydrochlor1c acid. -In this. case,--about, ten per.

cent. of water may be emfioyed. Whether sulfur trioxid or hydrocli oric acid be used to decompose the moist formate the yield will be' found to be practically theoretical if the temperature be carefully controlled.

lies between '15? C.- and 35 CL, the reaction greatly exceeding 35 C.

I claim posing the formic acid at temperatures ;The preferred temperature of the reaction being more sluggish at temperatures below 2 15 (3., and'thei'e'being llability of decom- 1; In a process of producing formic acid,

the, method which consists in reacting upon -a 'for'mateiin presence ofwater with a gase- ,ous reagent capable of displacing ihe formic acid by'combining with the base cfif the formate, thereby liberating formic acid. y

2..In-a process of producing'formio acid, the method which consists in bringing gaseous sulfur trioxid into reacting relation with -aformate in presence of sufficient water to convert the sulfur trioxid into sulfuric acid.

3. In a process of producing formic acid,

the method which consists in bringing gaseous sulfur trioxid into'reacting relation with a formats in presence of sufficient water to convert the sulfur trioxid into sulfuric acid while controlling the temperature of the I sired dilution may beprepared by using a."

corresponding excess of water. The formic reaction. I I 4. In a process of producing formic acid,

. a formate in presence of Water in approxithe method which consists in bringing gasethemethod which consists in bringing gasel mately the proportion required to convert 10 ous sulfur trioxid into reacting relation with l the sulfur trioxid into sulfuric acid While 5 controlling the temperature of the reaction. mately the roportion required to convert In testimony whereof, I aflix my signa the sulfur trloxid intosulfuric acid. ture in presence of two witnesses. 5. In a process of producing formic acid, HENRY HOWARD.

\Vitnesses ROBERT J KI G, 0. BEZANSON.

ous sulfur trioxid into reacting-relation with a formate 1n presence of Water in approxl- 

